<style>
    #app img{
        width: 40px;
    }
    @keyframes fade {
        from {
            opacity: 1.0;
        }
        50% {
            opacity: 0.4;
        }
        to {
            opacity: 1.0;
        }
    }

    @-webkit-keyframes fade {
        from {
            opacity: 1.0;
        }
        50% {
            opacity: 0.4;
        }
        to {
            opacity: 1.0;
        }
    }
.headerBox {
    color: #fff;
    /* padding: 10px; */
    font-size: 15px;
    width: 0px;
    border-right: 1px solid green;
    height: 60px;
    animation: fade 600ms infinite;
    -webkit-animation: fade 600ms infinite;
}

</style>
<div id="app" contenteditable="true" style="width:300px;height:200px;border:1px solid #dddddd"></div>
<div class="headerBox"></div>
<script>
// let app = document.getElementById('app')
// let img = new Image()
// img.src = 'https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1557944739037&di=4420c9a73ffa7a7f1d1f18077e884a0f&imgtype=0&src=http%3A%2F%2Fimage.biaobaiju.com%2Fuploads%2F20180802%2F01%2F1533142807-qciIlawNZp.jpg'
// app.appendChild(img)
</script>